XMILE (pizza.cs.ucl.ac.uk/xmile/) is an XML-based imperative language. Its goal is to keep mobile information devices synchronized by providing updates without stopping execution. Programs written in XMILE are transferred in source form, then interpreted on the remote host, which has the interpreter implemented in Java. In XMILE's case, the interpreter is already existent/installed in the clients. In our case, the interpreter, implemented in XSLT, is bundled together with the program.
In his book C++/XML (New Riders Publishing, 2001), Fabio Arjona Arciniegas describes how to build interpreters for XML-based scripting languages.
In "Towards SMIL as a Foundation for Multimodal, Multimedia Applications" (published in the Proceedings of EUROSPEECH 2001), Jennifer L. Beckham, et al., introduce ReX, which is a simple reactive programming language based on XML.
Superx++ (xplusplus.sourceforge.net/indexPage.htm) is an XML-based object-oriented language whose runtime environment is developed using C++ by Kimanzi Mati.
Sending code over the Internet to be executed on client web browsers represents one more degree of freedom than what is currently available, which is that the language available in the browsers is fixed, and only programs written in that language, and data to be used by that program, are sent to the browser.
The possibility of bundling together the language processor with the program and data opens up tremendous opportunities, allowing special purpose languages to be developed and used without requiring the end users to install additional components to their web browser. This also largely eliminates compatibility problems stemming from the unstandardized nature of scripting (and other) languages built into web browsers currently in use.